Project Summary Adolescence and young adulthood is a critical period for the development of social anxiety, which is often linked to other mental health challenges such as depression, mood disorders, and substance abuse. Initial evidence suggests that interacting with animals can reduce stress and anxiety, but no research has tested whether this benefit extends to adolescents at risk for social anxiety disorder. Additionally, researchers and clinicians do not understand what mechanism is responsible for anxiety reduction in animal-assisted interventions (AAIs). Therefore, the objectives of this study are to explore the specific mechanisms by which interacting with a therapy dog reduces anxiety, and to test whether such an interaction reduces anxiety in adolescents with varying levels of social anxiety. The specific aims of this project are to (1) test the mechanisms by which AAIs reduce anxiety, and (2) determine if the anxiolytic effect of social and physical interaction is moderated by level of pre-existing social anxiety. To achieve these aims, 75 adolescents (age 13-17) will undergo a well-validated laboratory-based social evaluative stressor, the Trier Social Stress Task for Children, and be randomly assigned to one of three conditions: 1) no interaction with a dog (control condition), 2) social interaction only (no physical interaction) with a therapy dog; or 3) social interaction plus physical interaction with a therapy dog. Using a multivariate approach, three levels of outcome data will be collected: a) self- reported experience (anxiety), b) autonomic physiology (heart rate), and c) behavioral performance (error rates on mental math task). In addition, the interactions will be videotaped and behavioral coding will be used to explore the specific social behaviors between the participant and the dog that may predict anxiety reduction (such as frequency or type of social referencing or physical contact). The proposed study represents exploration into a novel method of expanding knowledge about how animal-assisted interventions can be a potentially effective strategy for anxiety reduction for adolescents with social anxiety. This work represents a critical step in translating a hypothesized effect into a new treatment option for those with social anxiety. Because anxiety is an affective disturbance that is a prevalent component of many mental health diagnoses, the findings of this study will have implications for other diagnostic categories (e.g., generalized anxiety disorder, depression, post- traumatic stress disorder). This study will also lay the groundwork for pursuing programmatic future research to explore the duration and breadth of the therapeutic benefits of AAIs.